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    Characterization of a novel lipase bound to the Geobacillus stearothermophilus AH22 membrane
    (Springer Heidelberg, 2025) Dincer, Barbaros; Iskender, Engin; Kizil, Demet; Adiguzel, Ahmet
    Lipases (EC 3.1.1.3), used in many industrial applications, hydrolyze tri-, di-, and monoglycerides to free fatty acids and glycerol. This study aimed to determine the capacity of Geobacillus stearothermophilus AH22 for membrane-bound lipase production and to identify the optimal medium for lipase production. Following the determination of certain parameters such as pH and temperature, where the produced membrane-bound lipase exhibits the best activity, the kinetic data, as Km and Vmax, were obtained in the presence of p-NPA (0.03 +/- 0.008 mM and 0.7 +/- 0.18 U), p-NPB (0.7 +/- 0.18 mM and 3.4 +/- 0.40 U), p-NPO (0.12 +/- 0.010 mM and 5.2 +/- 0.62 U), and p-NPL (0.01 +/- 0.003 mM and 0.8 +/- 0.15 U) substrates. The highest activity of AH22 membrane-bound lipase was observed at pH 9.0 in the presence of substrates, at temperatures ranging from 20 to 40 degrees C for substrates with low carbon chains fatty acids and from 50 to 60 degrees C for substrates with long carbon chains. Also, it was observed that the cells dried by lyophilization showed lipase activity after they were pulver-ized. However, in terms of reuse, it was determined that wet cells were more efficient than powdered cells. It was found that the activity of the AH22 membrane-bound lipase had not changed much in the presence of anions and cations but decreased significantly in the presence of detergents and beta-mercaptoethanol. The AH22 membrane-bound lipase can be directly used in other industrial areas where lipase is used, except for the detergent industry, without requiring additional and expensive processing such as purification or immobilization.